1. Field of the Invention
The present invention relates to a high-temperature secondary battery based energy storage and power compensation system.
2. Description of the Related Art
Conventionally, various energy storage systems for carrying out a peak shaving function as well as a load leveling function have been proposed. Although the proposed systems have been put into practical use in pumped storage hydro, none of the proposed systems has a power compensation function for compensating for a voltage sag or a service interruption, all of which are likely to happen suddenly in power supply systems.
Various electric power quality stabilizing apparatus formed by using semiconductor electric power conversion apparatuses capable of inhibiting harmonic distortion as well as voltage fluctuations have also been proposed. In fact, these electric power quality stabilizing apparatuses have been practically used in active filters and static Var compensator(SVC). Furthermore, to compensate for voltage sag and service interruption, UPSs have been proposed and have already been put into practical use. However, none of the apparatuses mentioned above has a peak shaving function or a load leveling function.
The present invention relates to a system which solves the above problems. It is an object of the present invention to provide an economical, high-temperature secondary battery based energy storage and power compensation system which has a peak shaving function and a load leveling function, as well as an electric power quality stabilizing function.
According to the present invention, there is provided a high-temperature secondary battery based energy storage and power compensation system, comprising an electric power supply system, an electric load, and an electric energy storage system including a high-temperature secondary battery and a power conversion system (PCS).
In the preferred embodiment, the electric power supply system, the electric load and the electric energy storage system are electrically connected, and when operating normally, electric power is supplied to the electric load while the electric energy storage system operates to effect peak shaving running and load leveling running.
In addition, a high speed switch is provided between the electric power supply system and the electric energy storage system such that when a voltage sag or a service interruption occurs in the electric power being supplied from the electric power supply system, the voltage sag is immediately detected, the circuit is temporarily shut off and electric power is immediately supplied from the electric energy storage system to the electric load in order to compensate for the voltage sag or the service interruption.
Further, according to the present invention, the high temperature secondary battery is preferably a sodium sulfur battery.
Moreover, in the preferred embodiment the energy storage system compensating for a voltage sag or a service interruption is a system capable of outputting a compensation electric power which is 3 to 8 times the rated electric power of the peak shaving running and the load leveling running.
In addition, according to the present invention, it is preferred that a back-up generator is connected to a circuit on the electric power compensation side of the high speed switch. Additionally, a voltage compensation controller is provided which is capable of detecting a circuit shut-down effected by the high speed switch, sending a command in accordance with the detection signal to cause the energy storage system to discharge electric power required by the load, and at the same time starting the back-up generator. Thereby if the electric power supply is not restored within a predetermined time period, the back-up generator is connected in parallel with the system, while at the same time the electric power supply from the energy storage system is stopped.
Furthermore, according to the present invention, it is preferred that an electric power supply system further comprises a control function capable of coping with a fluctuation derived from an accident such as a spike or a frequency fluctuation in the electric power by detecting immediately such an accident, and sending a signal based on detection to the electric energy storage system in order to compensate for the fluctuation.
Moreover, according to the present invention, it is preferred that spare high-temperature batteries connected in parallel with the module batteries are provided so as to compensate by switching module batteries to the spare batteries in a case when the module batteries fail.